Exemplary embodiments of the present disclosure relate to a gas turbine, and more particularly, to a gas turbine which includes a plurality of compressor rotors and turbine rotors connected to each other through a tie-bolt, and has a cooling air flow path formed on the circumference of the tie-bolt.
In general, a gas turbine refers to a kind of internal combustion engine which mixes fuel with air compressed at high pressure by a compressor, burn the mixture to generate high-temperature and high-pressure combustion gas, and expands the combustion gas to convert thermal energy into mechanical energy. The compressor and the turbine acquire rotary power from a rotor.
In such a compressor rotor and a turbine rotor, a plurality of rotor disks having a plurality of compressor blades arranged on the outer circumferential surfaces thereof are connected to each other so as to be integrally rotated. A plurality of turbine rotor disks having a plurality of turbine blades arranged on the outer circumferential surface thereof are connected to each other so as to be integrally rotated. The compressor rotor disks and the turbine rotor disks are fastened to each other through a tie-bolt extended through the central portions of the compressor rotor disks and the turbine rotor disks.
However, there is a trend that gas turbines are increasing in size and efficiency, and overall lengths of the gas turbines have also been increased. This makes it difficult to rotatably support the tie-bolt which is rotated at high speed with the compressor rotor and the turbine rotor of the turbine.
Furthermore, a support unit for the rotating tie-bolt may not be easily positioned in a space between the compressor rotor and the turbine rotor along the central axis of the gas turbine, that is, a space in which combustors are radially arranged on the outer circumference of the gas turbine.
As illustrated in FIG. 1, the rotor assembly 1 includes a compressor rotor 2 including a plurality of compressor rotor disks 21, a turbine rotor 3 including a plurality of turbine rotor disks 31, and a single tie-bolt 5 extended through the compressor rotor 2 and the turbine rotor 3. The compressor rotor 2 and the turbine rotor 3 are fastened to each other through the tie-bolt 5, a compressor-side rotor component 6, and a turbine-side rotor component 7. The tie-bolt 5 is supported by a support wheel 41 provided in a hollow shaft 4 which forcibly connects the compressor rotor 2 and the turbine rotor 3 to each other. The rotor assembly 1 has a problem in that it is difficult to form a flow path for transferring the low-temperature air extracted from the compressor rotor 2 to the turbine rotor 3 so as to utilize the low-temperature air as cooling air for the turbine rotor 3.
As illustrated in FIG. 2A, a compressor rotor 2 and a turbine rotor (not illustrated) are fastened through a tie-bolt 5 passing through the compressor rotor 2 including a plurality of compressor rotor disks 21 having a plurality of compressor blades 22 arranged on the outer circumferential surfaces thereof, similar to the structure illustrated in FIG. 1. Furthermore, two cooling air pipes P1 and P2 are arranged on the circumference of the tie-bolt 5 such that flow paths F1 and F2 of cooling air transferred from through-holes 23 at different positions of the compressor rotor 2 are formed on the circumference of the tie-bolt 5. In addition, two clamping members 8 are provided on the outer circumferential surface of the tie-bolt 5 and the outer circumferential surface of the inner cooling air pipe P1, respectively, in order to support the tie-bolt 5.
Referring also to FIG. 2B, each of the clamping members 8 includes a cylindrical support ring 81, a plurality of support arms 82 extended from the support ring 81, and a support surface 83 in contact with the inner circumferential surface of the inner pipe P1 and the inner circumferential surface of the outer pipe P2. A recess 84 forming the flow paths F1 and F2 of cooling air is formed between the respective support arms 82.
In the clamping member 8, however, the width or thickness of the support arms 82 or the number of the support arms 82 must be increased to maintain the stiffness of the support arms 82. Such a structure may serve as an element which directly interferes with the cooling air paths F1 and F2 provided in the cooling air pipes P1 and P2.
That is, since the clamping members 8 are arranged in the cooling air flow paths F1 and F2 and the tie-bolt and the clamping members are rotated at high speed, the support arms 82 having a constant width interfere with a cooling air flow.
Furthermore, it is difficult to transfer low-temperature and low-pressure air extracted from the compressor rotor at the front stage, in which the pressure is relatively low, to the turbine rotor without a separate pressurizing unit.